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What is software design?
Design identifies the how of the system Involves tradeoff analysis based on the requirements Useful even on small projects Indispensable on large projects Two-part interactive process Conceptual design Technical design TERM 2
Conceptual design
DEFINITION 2 Tells the customer exactly what the system would do Written in customer language No technical jargon Describes the function of the system Independent of implementation Linked to requirement documents TERM 3
Technical design
DEFINITION 3 Allows system builders to understand the actual hardware and software needed to solve customers problem Description of the major hardware components and their functions Hierarchy and function of the software components Describes the data structures and data flow TERM 4
Design
layers
DEFINITION 4 High-Level Design (Architecture) Low-Level Design Algorithms Data Structures Component Interfaces TERM 5
Design Challenges
DEFINITION 5 Trade-offs and priorities Involves restrictions Nondeterministic A heuristic process
Timeless design guidelines
1- Iterative Enhancement 2- Stepwise Refinement 3- Information Hiding TERM 7
cohesion
DEFINITION 7
The cohesion of a module is the extent to which its
individual components are needed to perform the same task
High cohesion is a desirable design quality attribute for
components: when a change is made, it is localized in a single unit TERM 8
Quality Attributes
DEFINITION 8 Cohesion Coupling Understandability Adaptability Traceability TERM 9
Coupling
DEFINITION 9 Coupling refers to the degree of interdependence between modules Loose coupling is a desirable quality: it means component changes are unlikely to affect others TERM 10
Quality Attributes: Adaptability
DEFINITION 10 A general estimate of how easy it is to change the design The design must be easy to change A design is adaptable if: Its components are loosely coupled Each component is highly cohesive It is well-documented and kept up-to-date There is an obvious correspondence between design levels (design visibility) To adapt a design, it must be traceable
